1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method of manufacturing the electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member.
2. Related Background Art
Electrophotographic photosensitive members using organic photoconductive substances (organic electrophotographic photosensitive members) have been intensively studied and developed in recent years.
The electrophotographic photosensitive member is basically composed of a support and a photosensitive layer formed on the substrate. In the case of the organic electrophotographic photosensitive member, a photosensitive layer is formed using a charge-generating substance and a charge-transporting substance as photoconductive substances and a resin for binding these substances (binder resin).
There are two types of layer structure of the photosensitive layer: a multilayer type and a monolayer type. In the multilayer type one, the function of charge generation and the function of charge transfer are separated (functionally separated) into a charge-generating layer and a charge-transporting layer, respectively. In the monolayer type one, a single layer is provided with both the function of charge generation and the function of charge transfer.
Most of electrophotographic photosensitive members employ a multilayer type photosensitive layer. In many cases, the charge-transporting layer is provided as the surface layer of the electrophotographic photosensitive members.
The image formation using an electrophotographic apparatus is generally carried out as described below.
First, an electrophotographic photosensitive member is electrostatically charged and the charged electrophotographic photosensitive member is then irradiated with exposure light, thereby forming an electrostatic latent image on the electrophotographic photosensitive member. Subsequently, the electrostatic latent image is developed with a toner-containing developer and a toner image thus formed is then transferred from the electrophotographic photosensitive member to a transfer material (such as paper). The transfer material with the transferred toner image is subjected to a process of an image fixation and then discharged from the apparatus to the outside. On the other hand, the electrophotographic photosensitive member after the transfer process is subjected to a cleaning process so that the transfer residual toner is removed from the member, and the member is then subjected to the removal of electricity if required, followed by subjecting the electrophotographic photosensitive member to a subsequent cycle of image formation.
Further, reflecting the needs of high image qualities in recent years, the number of electrophotographic apparatuses each employing spherical toner produced by a suspension polymerization method or an emulsion polymerization method has increased. For example, in a process of wiping out the transfer residual toner, a cleaning member (such as a cleaning blade), which is brought into contact with the electrophotographic photosensitive member, may hardly prevent the toner from slipping therethrough because of the surface smoothness of such spherical toner.
For alleviating the slip of toner, the cleaning member should be optimized on the basis of the specifications of an electrophotographic apparatus. In other words, there is a need of increasing the contact pressure of the cleaning member to be applied on the electrophotographic photosensitive member, the flexibility of the mounting angle of the cleaning member, or the flexibility of designing the configuration of the cleaning member.
Under the operation of an electrophotographic apparatus, a cleaning blade may abnormally slide on an electrophotographic photosensitive member and sometimes cause the so-called “blade turn-up” where the blade turns up.
The blade turn-up may tend to occur at an early stage after the setting of the electrophotographic apparatus before the accumulation of the transfer residual toner (it functions as a powder to impart slidability between the cleaning blade and the electrophotographic photosensitive member) on the contact boundary surface between the cleaning blade and the electrophotographic photosensitive member. When the material of the cleaning blade is an elastic rubber material, a high-temperature, high-humidity environment may tend to increase the frequency at which the turn-up of the blade occurs.
Therefore, for avoiding the generation of such blade turn-up, the addition of an additive to the surface layer of an electrophotographic photosensitive member may intensively improve the flexibility of blade design. For instance, the improvement may be attained by a method involving adding a compound as disclosed in Japanese Patent Application Laid-Open No. S62-014657.
However, the function of the additive is to improve the slidability of a cleaning blade to prevent it from turning up, so the additive has been also desired to be inactive to the electrophotographic properties of the electrophotographic photosensitive member (i.e., not prevent electric charge from moving through the photosensitive layer).
By the way, Japanese Patent Application Laid-Open No. S58-164656 discloses a fluorine graft polymer with a linear fluoroalkyl group.
Further, Japanese Patent Application Laid-Open No. 2003-012588 discloses a fluorine-containing polymer with a trifluoromethyl group on any one of its side chains and an ether structure.